Today's interesting discovery is that the c908 on the k230 (despite not really advertising it) supports Zicbom and the T-Head custom CMO stuff.
Apparently the Chinese documentation says it supports it but the English documentation just says "RISC-V Base Cache Management Operation ISA Extensions Version 1.0-rc2-2c97b28, 2021-11-05: Frozen.". In comparison, about a third of the user manual talks about the T-Head CMOs.
edit: I realise it is expected that the document would cover the custom stuff in far more detail, but for the other standard extensions it claims to support, it at least mentions that it supports the instruction and what it does.
https://occ-intl-prod.oss-ap-southeast-1.aliyuncs.com/resource//1699268369347/XuanTie-C908-UserManual.pdfMade for an interesting conversation on IRC with dramforever, revy and cyy this afternoon :)